The invention relates to a semiconductor component with a semiconductor body and to a method for producing it. For this purpose, the semiconductor body has first electrodes which contact first highly doped semiconductor zones and complementary-conduction body zones, surrounding the first semiconductor zones, in the semiconductor body. In addition, the semiconductor body has a second electrode which contacts a second highly doped semiconductor zone. Between the second semiconductor zone and the body zones, a drift zone is arranged. Furthermore, control electrodes are arranged on the semiconductor body which are insulated from the semiconductor body by a gate oxide and act on the body zones for controlling the semiconductor device.
During the driving of the semiconductor device, a dynamic avalanche effect or also a dynamic punch-through effect may occur at the main pn junction between body zone and drift zone, which have a negative effect on the semiconductor devices if, for example, the current caused by the dynamic avalanche or by the dynamic punch-through, respectively, is sufficiently large to drive the first highly doped zone into conduction. This is equivalent to a malfunction of the semiconductor device and may damage the semiconductor device or impair the EMC characteristic (Electromagnetic Compatibility characteristic).
Furthermore, field steepening can occur with an avalanche at the non-conducting main pn junction between the body zones and the drift zone and lead to high destructive avalanche current densities. In the case of semiconductor devices with trench gate electrodes, field steepening with avalanche can additionally lead to high avalanche current densities at the trench gate bottom and thus damage the semiconductor device. Structures which counteract this dynamic avalanche effect or also a dynamic punch-through effect at the non-conducting main pn junction between body zone and drift zone have hitherto not been known.
Furthermore, voltage peaks may occur during the cutting-off of semiconductor devices with a flooded body diode during the commutation process since the reverse current breaks severely during the cutting-off. Such an interruption is unwanted because this distinctly degrades the electromagnetic compatibility characteristic (EMC characteristic) of the semiconductor device in its application. In semiconductor devices, such a problem only occurs with nominal cut-off voltages above 70 volts, particularly above 150 volts. On the other hand, the background doping is so high at very low cut-off voltages that flooding of the low-doped region for accommodating the space charge zone in the cut-off case with electrons and holes scarcely occurs.
In addition, this problem of interruption of the reverse current during cutting-off occurs when during a diode operation of the semiconductor device, the channel which forms between the first highly doped semiconductor zone and the drift zone in the body zone cannot remain connected for the entire period because cut-off loading can occur at the semiconductor device, for example with a direct transition from the conducting body diode.
To counteract this effect, a pedestal zone with correspondingly great thickness and correspondingly lesser doping compared with the drift zone has hitherto been used in between the drift zone and the second highly doped semiconductor zone in such semiconductor devices so that such a current interruption is avoided and a gradual switching characteristic is achieved which is tolerable in the EMC characteristic. However, such a high-resistance, because low-doped pedestals are in between drift zone and second highly doped semiconductor zone increases the resistive conducting-state losses of a semiconductor device switching in such gradual manner.
For these and other reasons, there is a need for the present invention.